Header flotation

Abstract

The hydraulic circuit of the present invention allows flotation of the header without extensive use of accumulators and is readily adaptable to present open center hydraulic systems. The present invention is also adaptable to closed center hydraulic systems with or without flow compensation. The hydraulic system has a pump selectively connected with the header cylinder. Pressure within the header cylinders is automatically maintained at a constant level by fluid addition to the cylinder or by extracting fluid from the cylinders.

What is claimed is: 
     
       1. A hydraulic system for raising, lowering and floating an implement from an agricultural vehicle in engagement with the ground comprising: a pump providing pressurized fluid;   at least one single-acting cylinder supporting said implement and being selectively connected with said pump;   a raise valve having a first position connecting said cylinder with said pump;   a pilot raise valve for activating said raise valve;   a lowering valve having a first position for evacuating the fluid within said cylinder;   a pilot lowering valve for activating said lowering valve; and   hydraulic pressure regulating means connected with said cylinder when the implement is floating and adjustable to transfer a predetermined portion of the weight of the implement to the ground.   
     
     
       2. An apparatus as described in claim 1, wherein the agricultural vehicle is a combine and the implement is a header. 
     
     
       3. An apparatus as described in claim 1, wherein the pilot raise valve is a solenoid operated valve. 
     
     
       4. An apparatus as described in claim 1, wherein the pilot lowering valve is a solenoid operated valve. 
     
     
       5. An apparatus as described in claim 1, wherein there is inserted a check valve between said pump and said cylinder preventing flow from said cylinder toward said pump. 
     
     
       6. An apparatus as described in claim 1, wherein said pressure regulating means is connected with said cylinder when said pilot lowering valve is moved to activate said lowering valve to said lowering valve's first position. 
     
     
       7. An apparatus as described in claim 1, wherein said lowering valve is a metering type valve. 
     
     
       8. A hydraulic system for raising, lowering, and floating a header from a combine in engagement with the ground comprising: a pump providing pressurized fluid;   at least one single-acting cylinder supporting said header from said combine and being selectively connected with said pump;   a raise valve having a first position connecting said pump with said cylinder and a second position diverting fluid from said pump away from said cylinder;   a pilot raise valve for activating said raise valve;   a metering type lowering valve having a first position for evacuating the fluid from said cylinder and having a second position preventing the evacuation of fluid from said cylinder;   a pilot lowering valve activating said lowering valve;   a pressure regulating valve connected with said cylinder when said header is floating and adjustable to transfer a predetermined portion of the weight of the header to the ground.   
     
     
       9. An apparatus as described in claim 8, wherein said pilot raise valve and said pilot lowering valve are solenoid operated. 
     
     
       10. An apparatus as described in claim 8, wherein said pilot raise valve is connected with said raise valve by a raise pilot line and wherein movement of said pilot raise valve to a position restraining flow through said raise pilot line activates said raise valve from said second position to said first position. 
     
     
       11. An apparatus as described in claim 8, wherein said pilot lowering valve is connected by a lowering pilot line with said lowering valve and wherein movement of said pilot lowering valve to a position allowing flow through said lowering pilot line activates said lowering valve from said second to said first position. 
     
     
       12. An apparatus as described in claim 11, wherein movement of said pilot lowering valve to activate said lowering valve from said second to said first position, also connects said pressure regulating valve with said cylinders. 
     
     
       13. A hydraulic system for raising, lowering and floating a header from a combine in engagement with the ground comprising: a pump providing pressurized fluid;   a plurality of single-acting cylinders for supporting the header from the combine, said cylinders being selectively connected with said pump;   a check valve preventing flow from said cylinders toward said pump;   a raise valve having a first position connecting said pump with said cylinders and having a second position diverting flow from said pump away from said cylinders;   a solenoid operated pilot raise valve connected with said raise valve by a raise pilot line, said pilot raise valve being moveable to a position blocking flow in said raise pilot line to activate said raise valve to said first position;   a lowering valve having a first position for evacuating the fluid within said cylinders and a second position to prevent evacuating the fluid from said cylinders;   a solenoid operated pilot lowering valve connected with said lowering valve by a lowering pilot line, said pilot lowering valve being moveable to a position allowing flow through said lowering pilot line to activate said lowering valve to said first position; and   a pressure regulating valve connected with said cylinder when said pilot lowering valve is in a position allowing flow through said lowering pilot line, said pressure regulating valve being adjustable to transfer a predetermined portion of the weight of said header to the ground when the header is floating.   
     
     
       14. A closed center hydraulic system for floating an implement from an agricultural vehicle in engagement with the ground comprising: at least one single-acting cylinder supporting said implement;   pressure signal means providing a hydraulic signal related to the desired pressure setting within said cylinder for transferring a desired portion of the weight of the implement to the ground;   a pump for supplying pressurized fluid to said cylinder;   a pressurizing valve for selectively connecting said pump with said cylinder in response to the hydraulic signal of said pressure signal means; and   a depressurizing valve selectively evacuating the fluid from said cylinder in response to the signal of said pressure signal means.   
     
     
       15. An apparatus as described in claim 14, wherein the agricultural vehicle is a combine and the implement is a header. 
     
     
       16. An apparatus as described in claim 14, wherein said hydraulic system is pressure flow compensated having a sense line connecting with an outlet of said pressurizing valve. 
     
     
       17. An apparatus as described in claim 14, further comprising a first connecting valve between said pressure signal means and said pressurizing valve. 
     
     
       18. An apparatus as described in claim 14, further comprising a second connecting valve between said pressure signal means and said depressurizing valve. 
     
     
       19. An apparatus as described in claim 17, wherein said first connecting valve is solenoid operated. 
     
     
       20. An apparatus as described in claim 18, wherein said second connecting valve is solenoid operated. 
     
     
       21. An apparatus as described in claim 14, wherein said pressure signal means is a biased spool valve. 
     
     
       22. A closed center hydraulic system for floating an implement from an agricultural vehicle in engagement with the ground comprising: at least one single-acting cylinder supporting the implement;   an adjustable pressure signal valve providing a hydraulic signal related to the desired pressure setting within said cylinder for transferring a desired portion of the weight of the implement to the ground;   a pump for supplying pressurized fluid to said cylinder;   a pressurizing valve for selectively connecting said pump with said cylinder in response to the hydraulic signal of said pressure signal valve;   a first connecting valve between said pressure signal valve and said pressurizing valve allowing passage of the hydraulic signal from said pressure signal valve to said pressurizing valve;   a depressurizing valve selectively evacuating fluid from said cylinder in response to a signal of said pressure signal valve; and   a second connecting valve allowing passage of the hydraulic signal from said pressure signal valve to said depressurizing valve.   
     
     
       23. An agricultural combine with a closed center pressure flow compensated hydraulic system for floating the header in engagement with the ground comprising: at least one single-acting cylinder supporting the header;   an adjustable pressure signal valve providing a hydraulic signal related to the desired pressure setting within said cylinder for transferring a desired portion of the weight of the header to the ground;   a pump for supplying pressurized fluid to said cylinder;   a pressurizing valve for selectively connecting said pump with said cylinder in response to the hydraulic signal of said pressure signal valve;   a first connecting valve between said pressure signal valve and said pressurizing valve allowing passage of the hydraulic signal from said pressure signal valve to said pressurizing valve;   a depressurizing valve selectively evacuating fluid from said cylinder in response to a signal of said pressure signal valve; and   a second connecting valve allowing passage of the hydraulic signal from said pressure signal valve to said depressurizing valve.   
     
     
       24. An agricultural combine as described in claim 23, wherein said first and second connector valves are solenoid operated. 
     
     
       25. An apparatus as recited in claim 22, wherein said pressure signal valve is spring loaded and wherein the pressure signal connecting with said pressurizing valve and the pressure signal connecting with said depressurizing valve are opposing with one another.